Nonlinear effects in many-body van der Waals interactions

TL;DR

This paper introduces a Discrete Coupled Nonlinear Dipole method to analyze van der Waals interactions considering nonlinear optical effects, revealing complex dependencies on material properties and system configurations.

Contribution

It develops a novel nonlinear dipole approach to study dispersive forces, extending beyond linear response theory to include hyperpolarizabilities and anisotropy.

Findings

Nonlinear effects significantly influence vdW energy.

Distance and anisotropy affect nonlinear vdW interactions.

The method uncovers complex interplay of material properties.

Abstract

Van der Waals interactions are ubiquitous and they play an important role for the stability of materials. Current understanding of this type of coupling is based on linear response theory, while optical nonlinearities are rarely considered in this context. Many materials, however, exhibit strong optical nonlinear response, which prompts further evaluation of dispersive forces beyond linear response. Here we present a $\textit{Discrete Coupled Nonlinear Dipole}$ approach that takes into account linear and nonlinear properties of all dipolar nanoparticles in a given system. This method is based on a Hamiltonian for nonlinear dipoles, which we apply in different systems uncovering a complex interplay of distance, anisotropy, polarizibilities, and hyperpolarizabilities in the vdW energy. This investigation broadens our basic understanding of dispersive interactions, especially in the context of nonlinear materials.